Sprinkler devices are well known and well accepted devices for protection of homes, offices, factories, and the like, against fire.
Conventional sprinkler devices typically utilize a heat-sensitive element which may, for example, melt at a predetermined temperature enabling a valve to open and spray water upon a predetermined area protected by the sprinkler device. Such devices have the disadvantage of remaining open and being incapable of reclosing due to destruction of the meltable element.
The need as well as the desire to provide sprinkler devices with an on-off capability have led to the development of sprinkler devices which have the capability of opening responsive to an emergency condition and reclosing when the emergency condition terminates. Note, for example, U.S. Pat. No. 3,757,866 which has a pilot valve actuated by a bimetal disk which normally biases the pilot valve to a closed condition, sealing a control opening communicating between a chamber in which a piston is reciprocatingly mounted and an outlet opening. Water enters through an inlet opening and passes through a restricted opening in the center of the piston to fill the aforementioned closed chamber whereby equal water pressure is applied on opposite surfaces of the piston but with the larger surface area of the piston confronting the closed chamber, the piston is urged to the closed position, sealing a second opening communicating between said inlet and said outlet.
The bimetal opens the valve to unseal the control opening when ambient temperature reaches a predetermined level such as 185.degree. F. allowing water in the previously closed chamber to pass through the outlet opening abruptly dropping the pressure applied to the bottom surface of the piston enabling the piston to be moved to a position unsealing the opening between the inlet and outlet.
The valve reseals the control opening between the chamber and the outlet opening responsive to a reduced ambient temperature, typically of the order of 100.degree. F., whereupon the chamber is refilled causing the liquid pressure build-up within the chamber to move the piston back to the position resealing the opening communicating the inlet with the outlet.
The above system, which is described in detail, for example, in U.S. Pat. No. 3,757,866, has a disadvantage of requiring O-ring sealing devices to prevent liquid filling the chamber from reaching the outlet opening, thus increasing the forces required to move the piston to both the sealed and the unsealed positions. The O-rings increase the force needed to move the piston. In addition, the useful operating life of the O-rings is limited, necessitating frequent maintenance and repair. For example, the average shelf life of an O-ring is of the order of fifteen years whereas the average life of a sprinkler device is of the order of fifty years. In addition, the shape of the piston necessitates the provision of two sliding chambers of different diameter for slidably mounting the piston.
Other sprinkler devices having on-off capabilities similar in design to the above-mentioned patent include: U.S. Pat. Nos. 3,698,483; 3,791,450; 3,802,510; 3,848,676; 4,553,602; 4,706,758; 4,830,117 and 4,830,118. The devices of all the above-mentioned patents have the disadvantage of requiring O-ring seals, as well as independent biasing members.
U.S. Pat. No. 4,359,098, in addition to requiring O-ring seals and biasing members, further requires a flexible diaphragm which is subject to wearing and deterioration at a rate equal to or greater than that experienced by the O-rings.
An on-off sprinkler described in U.S. Pat. No. 5,303,778 overcomes the disadvantages of the above prior art by providing a device characterized by a design which provides an in-line control assembly having an intermediate region communicating the inlet of the device to the outlet and containing a reciprocating spool slidably mounted within said intermediate region and movable to a first position displaced from a spool seat surrounding the outlet and a second position engaging the spool seat to seal the outlet. An insert within said region slidably receives the spool and forms a top chamber between the top interior of the insert and the top surface of the spool which communicates with the inlet through a small diameter (i.e. "restricted") orifice.
Water entering the inlet passes through said orifice and through passageways provided between the insert and the interior region to apply pressure to the top and bottom surfaces of the spool. Although the pressure applied to the top and bottom surfaces of the spool are substantially equal, the force of gravity acting upon the spool urges the spool to said second position, sealing the outlet.
A valve controlled by a heat sensor selectively seals and unseals a control opening whose size (i.e. diameter) is significantly greater than the orifice opening in the insert. The control opening is unsealed responsive to a predetermined emergency condition allowing water in the top chamber to pass through the unsealed control opening at a rate faster than water can enter into the restricted opening within the insert thereby abruptly dropping the pressure within the top chamber substantially to zero whereupon the water pressure applied to the bottom surface of the spool displaces the spool from the seat surrounding the outlet to thereby spray the area served by the sprinkler device.
The control opening is reclosed when the emergency condition is terminated causing water entering the restricted opening in the insert to refill the top chamber. Although the pressure applied to the top and bottom surfaces of the spool is substantially equal, the orientation of the spool is such that a gravitational force urges the spool toward the second or closed position, resealing the outlet.
As an alternative embodiment, the spool may be provided with a top surface of greater surface area than the bottom surface to facilitate and enhance the closing operation and to facilitate maintaining the spool and hence the sprinkler device in the closed position. The opening operation is not affected by the modified spool.
Water in the top chamber is prevented from passing from the top chamber to the region surrounding the bottom surface of the spool and hence the outlet by controlling the gap region between the ID of the insert and the OD of the spool to a gap size which is sufficient to provide a watertight seal while enabling the spool to freely move between said first and second positions. This novel seal totally eliminates the need for conventional sliding seal members, such as O-rings, thereby eliminating the need for maintenance and replacement of such sliding seal members as is required in conventional sprinkler devices, as well as significantly reducing the frictional forces acting against the sliding movement of the spool. The novel, vertical, in-line arrangement of the spool takes advantage of gravitational forces, thus eliminating the need for conventional bias members, such as helical springs, or the like.
In an alternative embodiment, the spool may be either a cylindrical-shaped member or a spherical-shaped member.
In still another preferred embodiment, a sprinkler head assembly is mounted adjacent the outlet of the on-off sprinkler device and is provided with a blocking bar which blocks the spool (or ball) from sealing the outlet until the sprinkler device is actuated. This arrangement provides a fail-safe design in the event of a corrosion related failure of the on-off sprinkler device by assuring that the spool would be stuck in the open (i.e. fail-safe) position rather than the closed position.
Although the on-off sprinkler disclosed in U.S. Pat. No. 5,303,778 is superior in most respects to the above-mentioned prior art, is suspected that sediment or particulate or other foreign matter carried by the fluid passing through the sprinkler may collect in the gap, which may restrict the free movement of the reciprocating spool.